Silicon spin diffusion transistor: materials, physics and device characteristics

The realisation that eaveryday electronics has ignored the spin of the carrier in favour of its charge is the foundation of the field of spintronics. Starting with simple two-terminal devices based on GMR and tunnel magnetoresistance, the technology has advanced to consider three-terminal devices that aim to combine spin sensitivity with a high current gain and a large current output. These devices require both efficient spin injection and semiconductor fabrication. In this paper, a discussion is presented of the design, operation and characteristics of the only spin transistor that has yielded a current gain greater than one in combination with reasonable output current

Switching ferroelectric domain configurations using both electric and magnetic fields in Pb(Zr,Ti)O3–Pb(Fe,Ta)O3 single-crystal lamellae

Thin single-crystal lamellae cut from Pb(Zr,Ti)O(3)–Pb(Fe,Ta)O(3) ceramic samples have been integrated into simple coplanar capacitor devices. The influence of applied electric and magnetic fields on ferroelectric domain configurations has been mapped, using piezoresponse force microscopy. The extent to which magnetic fields alter the ferroelectric domains was found to be strongly history dependent: after switching had been induced by applying electric fields, the susceptibility of the domains to change under a magnetic field (the effective magnetoelectric coupling parameter) was large. Such large, magnetic field-induced changes resulted in a remanent domain state very similar to the remanent state induced by an electric field. Subsequent magnetic field reversal induced more modest ferroelectric switching

Magnetic switching of ferroelectric domains at room temperature in multiferroic PZTFT

Single-phase magnetoelectric multiferroics are ferroelectric materials that display some form of magnetism. In addition, magnetic and ferroelectric order parameters are not independent of one another. Thus, the application of either an electric or magnetic field simultaneously alters both the electrical dipole configuration and the magnetic state of the material. The technological possibilities that could arise from magnetoelectric multiferroics are considerable and a range of functional devices has already been envisioned. Realising these devices, however, requires coupling effects to be significant and to occur at room temperature. Although such characteristics can be created in piezoelectric-magnetostrictive composites, to date they have only been weakly evident in single-phase multiferroics. Here in a newly discovered room temperature multiferroic, we demonstrate significant room temperature coupling by monitoring changes in ferroelectric domain patterns induced by magnetic fields. An order of magnitude estimate of the effective coupling coefficient suggests a value of ~1 × 10(−7) sm(−1)

Angular dependence of domain wall resistivity in SrRuO3_{{\bf 3}} films

${\rm SrRuO_3}$ is a 4d itinerant ferromagnet (T$_{c}$ $\sim$150 K) with stripe domain structure. Using high-quality thin films of SrRuO$_{3}$ we study the resistivity induced by its very narrow ($\sim 3$ nm) Bloch domain walls, $\rho_{DW}$ (DWR), at temperatures between 2 K and T$_{c}$ as a function of the angle, $\theta$, between the electric current and the ferromagnetic domains walls. We find that $\rho_{DW}(T,\theta)=\sin^2\theta \rho_{DW}(T,90)+B(\theta)\rho_{DW}(T,0)$ which provides the first experimental indication that the angular dependence of spin accumulation contribution to DWR is $\sin^2\theta$. We expect magnetic multilayers to exhibit a similar behavior.Comment: 5 pages, 5 figure

Nonequilibrium ferroelectric-ferroelastic 10-nm nanodomains : wrinkles, period-doubling, and power-law relaxation

Since the 1935 work of Landau and Lifshitz and of Kittel in 1946 all ferromagnetic, ferroelectric, and ferroelastic domains have been thought to be straight-sided with domain widths proportional to the square root of the sample thickness. We show in the present work that this is not true. We also discover period doubling domains predicted by Metaxas et al. (Phys. Rev. Lett. 2008, 217208) and modeled by Wang and Zhao Q. (Sci. Rpts. 2015, 5, 8887). We examine non-equilibrium ferroic domain structures in perovskite oxides with respect to folding, wrinkling, and relaxation and suggest that structures are kinetically limited and in the viscous flow regime predicted by Metaxas et al. in 2008 but never observed experimentally. Comparisons are made with liquid crystals and hydrodynamic instabilities, including chevrons, and fractional power-law relaxation. As Shin et al. [Soft Mat. 2016, 12, 3502] recently emphasized: “An understanding of how these folds initiate, propagate, and interact with each other is still lacking.” Inside each ferroelastic domain are ferroelectric 90-degree nano-domains with 10-nm widths and periodicity in agreement with the 10-nm theoretical minima predicted by Feigl et al. (Nat. Commun. 2014, 5, 4677). Evidence is presented for domain-width period doubling, which is common in polymer films but unknown in ferroic domains. A discussion of the folding-to-period doubling phase transition model of Wang and Zhao is included.PostprintPeer reviewe

Effect of a Domain Wall on the Conductance Quantization in a Ferromagnetic Nanowire

The effect of the domain wall (DW) on the conductance in a ballistic ferromagnetic nanowire (FMNW) is revisited by exploiting a specific perturbation theory which is effective for a thin DW; the thinness is often the case in currently interested conductance measurements on FMNWs. Including the Hund coupling between carrier spins and local spins in a DW, the conductance of a FMNW in the presence of a very thin DW is calculated within the Landauer-B\"{u}ttiker formalism. It is revealed that the conductance plateaus are modified significantly, and the switching of the quantization unit from $e^2/h$ to ``about $2e^2/h$'' is produced in a FMNW by the introduction of a thin DW. This accounts well for recent observations in a FMNW.Comment: 5 pages, 2 figures, Corrected typos and added reference

Electronic transport through domain walls in ferromagnetic nanowires: Co-existence of adiabatic and non-adiabatic spin dynamics

We study the effect of a domain wall on the electronic transport in ferromagnetic quantum wires. Due to the transverse confinement, conduction channels arise. In the presence of a domain wall, spin up and spin down electrons in these channels become coupled. For very short domain walls or at high longitudinal kinetic energy, this coupling is weak, leads to very few spin flips, and a perturbative treatment is possible. For very long domain wall structures, the spin follows adiabatically the local magnetization orientation, suppressing the effect of the domain wall on the total transmission, but reversing the spin of the electrons. In the intermediate regime, we numerically investigate the spin-dependent transport behavior for different shapes of the domain wall. We find that the knowledge of the precise shape of the domain wall is not crucial for determining the qualitative behavior. For parameters appropriate for experiments, electrons with low longitudinal energy are transmitted adiabatically while the electrons at high longitudinal energy are essentially unaffected by the domain wall. Taking this co-existence of different regimes into account is important for the understanding of recent experiments.Comment: 10 pages, 6 figure

Reflection of electrons from a domain wall in magnetic nanojunctions

Electronic transport through thin and laterally constrained domain walls in ferromagnetic nanojunctions is analyzed theoretically. The description is formulated in the basis of scattering states. The resistance of the domain wall is calculated in the regime of strong electron reflection from the wall. It is shown that the corresponding magnetoresistance can be large, which is in a qualitative agreement with recent experimental observations. We also calculate the spin current flowing through the wall and the spin polarization of electron gas due to reflections from the domain wall.Comment: 7 pages, 4 figure

Ballistic electron transport through magnetic domain walls

Electron transport limited by the rotating exchange-potential of domain walls is calculated in the ballistic limit for the itinerant ferromagnets Fe, Co, and Ni. When realistic band structures are used, the domain wall magnetoresistance is enhanced by orders of magnitude compared to the results for previously studied two-band models. Increasing the pitch of a domain wall by confinement in a nano-structured point contact is predicted to give rise to a strongly enhanced magnetoresistance.Comment: 4 pages, 2 figures; to appear in PRB as a brief repor

Impact of left ventricular ejection fraction on clinical outcomes after left main coronary artery revascularization

Aim: To evaluate the impact of left ventricular ejection fraction (LVEF) on 3-year outcomes in patients with left main coronary artery disease (LMCAD) undergoing percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG) in the EXCEL trial. Methods and results: The EXCEL trial randomized patients with LMCAD to PCI with everolimus-eluting stents (n = 948) or CABG (n = 957). Among 1804 patients with known baseline LVEF, 74 (4.1%) had LVEF <40% [heart failure with reduced ejection fraction (HFrEF)], 152 (8.4%) LVEF 40–49% [heart failure with mid-range ejection fraction (HFmrEF)] and 1578 (87.5%) LVEF ≥50% (heart failure with preserved ejection fraction). Patients with HFrEF vs. HFmrEF vs. preserved LVEF experienced a longer postoperative hospital stay (9.0 vs. 7.0 vs. 6.0 days, P = 0.02) with greater peri-procedural complications after CABG, while hospital stay after PCI was unaffected by LVEF (1.5 vs. 2.0 vs. 1.0 days, P = 0.20). The composite primary endpoint of death, stroke, or myocardial infarction at 3 years was 29.3% (PCI) vs. 27.6% (CABG) in patients with HFrEF, 16.2% vs. 15.0% in patients with HFmrEF, and 14.5% vs. 14.6% in those with preserved LVEF, respectively (Pinteraction = 0.90). Smoothing spline analysis demonstrated that the 3-year risk of all-cause death increased when LVEF decreased, both in patients undergoing CABG and PCI. Conclusion: In the EXCEL trial, the composite rate of death, stroke or myocardial infarction at 3 years was significantly higher in patients with HFrEF compared with HFmrEF or preserved LVEF, driven by an increased rate of all-cause death. No significant differences after PCI vs. CABG were observed among patients with HFrEF, HFmrEF and preserved LVEF. Longer-term follow-up could provide important insights on differences in clinical outcomes that might emerge over time. Clinical Trial Registration: ClinicalTrials.gov ID NCT01205776